Nozzle arrangement for an inkjet printhead having dynamic and static structures to facilitate ink ejection

ABSTRACT

Provided is a nozzle arrangement for an inkjet printhead. The nozzle arrangement includes a substrate with side walls and a roof portion together forming an ink chamber, the substrate defining an ink supply channel leading to the ink chamber, with one side wall defining an aperture. The arrangement also includes an elongate actuator extending through said aperture into the ink chamber, as well as a dynamic structure cantilevered from the side wall below the aperture. Further included is a static structure cantilevered from the side wall below the dynamic structure. The actuator is connected to the dynamic and static structures at a point distal from the aperture such that thermal expansion of the dynamic structure moves the actuator upwards in the chamber to eject ink from the chamber via a port defined in the roof portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation of U.S. application Ser. No. 11/583,895 filedOct. 20, 2006 now U.S. Pat. No. 7,461,923, which is a Continuation ofU.S. application Ser. No. 11/450,585 filed Jun. 12, 2006, now issuedU.S. Pat. No. 7,137,686 which is a continuation of U.S. application Ser.No. 11/165,055 filed Jun. 24, 2005, now issued U.S. Pat. No. 7,066,578,which is a Continuation of U.S. application Ser. No. 10/698,412 filedNov. 3, 2003, now issued U.S. Pat. No. 6,935,724, which is aContinuation-In-Part of U.S. Ser. No. 10/160,273 filed on Jun. 4, 2002,now issued U.S. Pat. No. 6,746,105, which is a Continuation Applicationof U.S. Ser. No. 09/112,767 filed on Jul. 10, 1998, now issued U.S. Pat.No. 6,416,167 all of which are herein incorporated by reference.

FIELD OF INVENTION

The present invention relates to a nozzle arrangement for amicroelectromechanical system (‘MEMS’) inkjet printhead.

BACKGROUND OF THE INVENTION

In the MEMS nozzle arrangement described in U.S. Pat. No. 6,243,113“Image Creation Method and Apparatus” (the contents of which areincorporated herein by cross reference), an ink chamber is provided withan ink inlet and an ink ejection port, which are coaxial. The inkejection port is provided through thermal actuator that incorporates apaddle mounted to a substrate by a passive anchor and an active anchor.The active anchor includes a resistive element that heats up uponapplication of a current. This heating causes expansion of the activeanchor, whilst the passive anchor is sufficiently shielded from thegenerated heat that it remains the same length. The change in relativelengths of the anchors is amplified by the geometric position of theanchors with respect to each other, such that the paddle can selectivelybe displaced with respect to the ink chamber by applying a suitabledrive current to the active anchor.

Upon actuation, the paddle is urged towards the ink chamber, causing anincrease in pressure in the ink in the chamber. This in turn causes inkto bulge out of the ink ejection port. When the drive current isremoved, the active anchor quickly cools, which in turn causes thepaddle to return to its quiescent position. The inertia of the movingink bulge causes a thinning and breaking of the ink surface adjacent theink ejection port, such that a droplet of ink continues moving away fromthe port as the paddle moves back to its quiescent position. As thequiescent position is reached, surface tension of a concave meniscusacross the ink ejection port causes ink to be drawn in to refill the inkchamber via the ink inlet. Once the ink chamber is full, the process canbe repeated.

One difficulty with prior art devices of this type is that the actuatorsadd to the total surface area required for each nozzle. It would bedesirable to reduce the surface area required for each nozzlearrangement, since this would allow increased nozzle arrangement densityon a printhead.

SUMMARY OF INVENTION

In accordance with the invention, there is provided a nozzle arrangementfor an inkjet printhead, the nozzle arrangement including:

(a) a nozzle chamber for holding ink;

(b) a passive anchor and an active anchor extending from respectiveanchor points;

(c) a moveable structure including a portion in fluid communication withthe ink chamber, the moveable structure being connected to the passiveand active anchors at connection points distal the respective anchorpoints such that actuation of the active anchor causes displacement ofthe portion with respect to the ink chamber;(d) a fluid ejection port in fluid communication with the ink chamberfor enabling ejection of ink from the chamber by the portion uponactuation of the active anchor;

-   -   wherein the anchor point of at least one of the active and        passive anchors is positioned between the nozzle chamber and the        connection points.

Preferably, the moveable structure is moved within a first action planeupon actuation. More preferably, the movement includes a rotationalcomponent.

In a preferred embodiment, the active anchor is a thermal actuatorconfigured to expand due to self-heating when a current is passedtherethrough. Preferably, the active anchor is a thermal bend actuator.It is particularly preferred that there is provided more than one ofeach of the passive and/or active anchors.

Preferably, the moveable structure is supported at least in part by thepassive and active anchors. More preferably, ink in the chamber providesfluidic support to the moveable structure by way of surface tensionand/or fluid pressure.

In a preferred embodiment, the active anchor is configured to supply,upon actuation, a compressive force between its anchor point andconnection point. Preferably, the compressive force is suppliedsubstantially parallel to the plane.

Other preferred aspects, features and embodiments of the invention aredescribed in the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 shows a plan view of an ink jet printhead chip of the invention.

FIG. 2 shows a plan view of one nozzle arrangement of the ink jetprinthead chip.

FIG. 3 shows a sectioned view of the nozzle arrangement taken throughC-C in FIG. 2.

FIG. 4 shows a three-dimensional sectioned view of the nozzlearrangement.

FIG. 5 shows a side sectioned view of the nozzle arrangement in apre-ejection quiescent condition.

FIG. 6 shows a side sectioned view of the nozzle arrangement of FIG. 2in an operative condition.

FIG. 7 shows a side sectioned view of the nozzle arrangement of FIG. 2in a post-ejection quiescent condition.

FIG. 8 shows a three-dimensional view through A-A in FIG. 10 of a wafersubstrate, a drive circuitry layer, contact pads and an ink passivationlayer for a starting stage in the fabrication of each nozzle arrangementof the printhead chip.

FIG. 9 shows a sectioned view through B-B in FIG. 10 of the stage ofFIG. 8.

FIG. 10 shows a mask used for patterning the ink passivation (siliconnitride) layer.

FIG. 11 shows a three-dimensional view through A-A in FIG. 13 of thestage of FIG. 8 with a resist layer deposited and patterned on the inkpassivation layer.

FIG. 12 shows a side sectioned view through B-B in FIG. 13 of the stageof FIG. 11.

FIG. 13 shows a mask used for patterning the resist layer of FIG. 11.

FIG. 14 shows a three-dimensional view sectioned view of the stage ofFIG. 11, with the resist layer removed and the wafer substrate etched toa predetermined depth to define an ink inlet channel of the nozzlearrangement.

FIG. 15 shows a side sectioned view of the stage of FIG. 14.

FIG. 16 shows a three-dimensional sectioned view through A-A in FIG. 18of the stage of FIG. 14 with a first sacrificial layer deposited andpatterned on the ink passivation layer.

FIG. 17 shows a side sectioned view through B-B in FIG. 18 of the stageof FIG. 16.

FIG. 18 shows a mask used for patterning the first sacrificial layer.

FIG. 19 shows a three-dimensional sectioned view through A-A in FIG. 21of the stage of FIG. 16 with a second sacrificial layer deposited andpatterned on the first sacrificial layer.

FIG. 20 shows a side sectioned view through B-B in FIG. 21 of the stageof FIG. 19.

FIG. 21 shows a mask used for patterning the second sacrificial layer.

FIG. 22 shows a three-dimensional view through A-A in FIG. 24 of thestage of FIG. 19 after a selective etching of the second sacrificiallayer.

FIG. 23 shows a side sectioned view through B-B in FIG. 24 of the stageof FIG. 22.

FIG. 24 shows a mask used for the selective etching of the secondsacrificial layer.

FIG. 25 shows a three-dimensional view of the stage of FIG. 21 with aconductive layer deposited on the second sacrificial layer.

FIG. 26 shows a side sectioned view of the stage of FIG. 25.

FIG. 27 shows a sectioned three-dimensional view through A-A in FIG. 29of the stage of FIG. 25 with the conductive layer subjected to aselective etch.

FIG. 28 shows a side sectioned view through B-B of the stage of FIG. 27.

FIG. 29 shows a mask used for the etching of the conductive layer.

FIG. 30 shows a three-dimensional sectioned view through A-A in FIG. 32with a third layer of sacrificial material deposited on the etchedconductive layer.

FIG. 31 shows a sectioned side view through B-B in FIG. 32 of the stageof FIG. 30.

FIG. 32 shows a mask used for the deposition of the third sacrificiallayer.

FIG. 33 shows a three-dimensional view of the stage of FIG. 28 with alayer of titanium deposited on the third layer of sacrificial material.

FIG. 34 shows a side sectioned view of the stage of FIG. 33.

FIG. 35 shows a three-dimensional sectioned view taken through A-A inFIG. 37 of the layer of titanium subjected to an etch.

FIG. 36 shows a side sectioned view through B-B in FIG. 37 of the stageof FIG. 35.

FIG. 37 shows a mask used for etching the layer of titanium.

FIG. 38 shows a three-dimensional view of the stage of FIG. 35 with alayer of dielectric material deposited on the etched layer of titanium.

FIG. 39 shows a side sectioned view of the stage of FIG. 38.

FIG. 40 shows a three-dimensional sectioned view through A-A in FIG. 42of the stage of FIG. 38 after a selective etching of the dielectriclayer.

FIG. 41 shows a side sectioned view through B-B in FIG. 42 of the stageof FIG. 40.

FIG. 42 shows a mask used in the selective etching of the dielectriclayer.

FIG. 43 shows a three-dimensional sectioned view through A-A in FIG. 45of the stage of FIG. 40 after a further selective etching of thedielectric layer.

FIG. 44 shows a side sectioned view through B-B in FIG. 45.

FIG. 45 shows a mask used for the further selective etching of thedielectric layer.

FIG. 46 shows a three-dimensional sectioned view through A-A in FIG. 48of the stage of FIG. 43 with a resist layer deposited on the dielectriclayer and subsequent to a preliminary back etching of the wafersubstrate.

FIG. 47 shows a side sectioned view taken through B-B in FIG. 48 of thestage of FIG. 46.

FIG. 48 shows a mask used for the preliminary back etching of the wafersubstrate.

FIG. 49 shows a three-dimensional sectioned view of the stage of FIG. 46subsequent to a secondary back etching of the material of the firstsacrificial layer positioned in an inlet and nozzle chamber of thenozzle arrangement.

FIG. 50 shows a side sectioned view of the stage of FIG. 49.

FIG. 51 shows three-dimensional sectioned view of the stage of FIG. 49with all the sacrificial material and resist material removed.

FIG. 52 shows a side sectioned view of the stage of FIG. 51.

FIG. 53 shows a simplified, side sectioned view of an alternativeembodiment of a nozzle arrangement according to the invention.

FIG. 54 shows a side sectioned view of the nozzle arrangement of FIG. 53during actuation.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIGS. 1 to 7, reference numeral 10 generally indicates a nozzlearrangement for an ink jet print head chip 12, part of which is shown inFIG. 1.

The nozzle arrangement 10 is the product of an integrated circuitfabrication technique. In particular, the nozzle arrangement 10 definesa micro-electromechanical system (MEMS).

In this description, only one nozzle arrangement 10 is described. Thisis simply for clarity and ease of description. A print head having oneor more print head chips 12 can incorporate up to 84000 nozzlearrangements 10. Further, as is clear from FIG. 1, the print head chip12 is a multiple replication of the nozzle arrangement 10. It followsthat the following detailed description of the nozzle arrangement 10 andthe manner of its fabrication adequately describes the print head chip12.

The ink jet print head chip 12 includes a silicon wafer substrate 14.0.35 Micron 1 P4M 12 volt CMOS microprocessing circuitry is positionedon the silicon wafer substrate 14. The circuitry is shown as a drivecircuitry layer 16.

A silicon dioxide or glass layer 18 is positioned on the wafer substrate14. The layer 18 defines CMOS dielectric layers. CMOS top-level metaldefines a pair of aligned aluminum electrode contact layers 20positioned on the silicon dioxide layer 18. Both the silicon wafersubstrate 14 and the silicon dioxide layer 18 are etched to define anink inlet channel 22 having a circular cross section. An aluminumdiffusion barrier 24 of CMOS metal 1, CMOS metal 2/3 and CMOS top levelmetal is positioned in the silicon dioxide layer 18 about the ink inletchannel 22. The barrier 24 serves to inhibit the diffusion of hydroxylions through CMOS oxide layers of the drive circuitry layer 16.

A portion of the diffusion barrier 24 extends from the silicon dioxidelayer 18. An ink passivation layer in the form of a layer of siliconnitride 26 is positioned over the aluminum contact layers 20 and thesilicon dioxide layer 18, as well as the diffusion barrier 24. Eachportion of the layer 26 positioned over the contact layers has anopening 28 defined therein to provide access to the contacts 20.

The nozzle arrangement 10 includes a static structure 40 and a dynamicstructure 42 that together define a nozzle chamber 34. The staticstructure 40 defines a fixed part 36 of a nozzle chamber wall 30 thatextends from the layer 26 of silicon nitride and bounds the ink inletchannel 22. The dynamic structure 42 defines a movable part 38 of thenozzle chamber wall 30 and a roof wall 32. The roof wall 32 defines anink ejection port 44.

The movable part 38 of the nozzle chamber wall 30 overlaps the fixedpart 36 of the nozzle chamber wall 30. The fixed part 36 defines aninwardly directed lip 46 that extends into the nozzle chamber 34. Thefixed part 36 also defines an outwardly directed, re-entrant portion 48that terminates in a radially extending rim 50. The movable part 38depends from the roof wall 32 and terminates at a free edge 52.

As can be seen in FIGS. 5 and 7, the free edge 52 is aligned with therim 50 when the nozzle arrangement 10 is in a quiescent condition. Ascan be seen in FIG. 6, the free edge 52 extends past the rim 50 when thenozzle arrangement 10 is in an operative condition. A meniscus 54extends from the rim 50 to the free edge 52 when the nozzle chamber 34is filled with ink 56. As can be seen in the FIGS., the meniscus 54 isstretched to accommodate movement of the dynamic structure 42 towardsand away from the substrate 14. It will be appreciated that thedimensions of the components that make up the nozzle arrangement 10 aremicroscopic. At this scale, surface tension effects are significantenough to inhibit leakage of ink 56 between the rim 50 and the free edge52. It follows that when the nozzle chamber 34 is filled with the ink56, the rim 50 and the free edge 52 define a fluidic seal.

As shown in FIGS. 5 to 7, when the dynamic structure 42 is urged towardsthe substrate 14, an ink drop 58 is formed. When the dynamic structure42 returns to a quiescent condition, the ink drop 58 separates from theink 56 in the nozzle chamber 34 and the nozzle chamber 34 is refilledwith ink 56.

A thermal actuator 60 is electrically connected to both the contactlayers at the openings 28. The openings 28 are positioned between theink inlet channel 22 and one side 62 of the nozzle arrangement 10. Theopenings 28 are positioned closer to the ink inlet channel 22 than tothe side 62. The thermal actuator 60 is of titanium aluminum nitride.Further, the thermal actuator 60 has four anchor portions 64 that extendfrom the silicon nitride layer 26 to a predetermined point spaced fromthe silicon nitride layer 26. The anchor portions 64 are alignedtransversely with respect to the substrate 14. The anchor portions 64define a pair of active anchor portions 64.1 positioned between a pairof spaced passive anchor portions 64.2.

Each of the active anchor portions 64.1 is positioned at respectiveopenings 28. Further, each active anchor portion 64.1 is electricallyconnected to one respective contact 20 to define a via 66. Each via 66includes a titanium layer 68 and the active anchor portion 64.1sandwiched between a layer 70 of dielectric material in the form of lowtemperature silicon nitride and one respective contact 20.

Each of the passive anchor portions 64.2 is retained in position bybeing sandwiched between the layer 70 of low temperature silicon nitrideand the silicon nitride layer 26. Generally, the structure of the activeanchor portions 64.1 and the vias 66 are similar to the structure of thelayer 70 in combination with the passive anchor portions 64.2. However,the absence of the openings 28 at the passive anchor portions 64.2ensures that electrical contact between the thermal actuator 60 and thecontacts 20 is not made. This is enhanced by the fact that siliconnitride is a dielectric material.

Details of the thermal actuator 60 are shown in FIGS. 2 to 7. Thethermal actuator 60 includes a pair of inner actuator arms 72 and a pairof outer actuator arms 74. Each inner actuator arm 72 is connected to afree end of a respective active anchor portion 64.1. Similarly, eachouter actuator arm 74 is connected to a free end of a respective passiveanchor portion 64.2. The actuator arms 72, 74 extend from the anchorportions 64 in a plane that is generally parallel to a plane of thewafer substrate 14, towards the one side 62 of the nozzle arrangement10. The actuator arms 72, 74 terminate at a common bridge portion 76.

Each inner actuator arm 72 includes a planar section 80 that ispositioned in a plane parallel to that of the wafer substrate 14. Eachouter actuator arm 74 includes a planar section 82 that is positioned ina plane parallel to that of the wafer substrate 14. The bridge portion76 interconnects the planar sections 80, 82.

The arms 72, 74 and the bridge portion 76 are configured so that, when apredetermined electrical current is applied to the inner actuator arms72, the inner actuator arms 72 are heated to the substantial exclusionof the outer actuator arms 74. This heating results in an expansion ofthe inner actuator arms 72, also to the exclusion of the outer actuatorarms 74. As a result, a differential expansion is set up in the actuatorarms 72, 74. The differential expansion results in the actuator arms 72,74 bending away from the layer 26 of silicon nitride.

A layer 84 of titanium is positioned on the bridge portion 76. A layer86 of dielectric material in the form of low temperature silicon nitrideis positioned on the layer 84. This layer 86 is connected to, and formspart of, the layer 70 to define a lever arm structure 88. A layer 90 ofdielectric material defines the roof wall 32. The layer 90 forms partof, and is connected to, the layer 86. The anchor portions 64, thetitanium layers 68 and the layer 70 of dielectric material define afulcrum formation 92. Thus, the dynamic structure 42 is displacedtowards the substrate 14 when the actuator 60 is displaced away from thesubstrate 14. It follows that resultant differential expansion causesthe actuator 60 to move away from the substrate 14 and the roof wall 32to compress the ink 56 in the nozzle chamber 34 so that the ink drop 58is ejected when an electrical current is set up in the actuator 60.Differential contraction causes the actuator 60 to move towards thesubstrate 14 and the roof wall 32 to move upwards, separating the drop58.

A nozzle rim 94 bounds the ink ejection port 44. A plurality of radiallyextending recesses 96 is defined in the roof wall 32 about the rim 94.These serve to contain radial ink flow as a result of ink escaping pastthe nozzle rim 94.

The nozzle arrangement 10 includes a test switch arrangement 98. Thetest switch arrangement 98 includes a pair of titanium aluminum nitridecontacts 100 that is connected to test circuitry (not shown) and ispositioned at a predetermined distance from the wafer substrate 14. Thedynamic structure 42 includes an extended portion 102 that is opposed tothe fulcrum formation 92 with respect to the roof wall 32. A titaniumbridging member 104 is positioned on the extended portion 102 so that,when the dynamic structure 42 is displaced to a maximum extent towardsthe wafer substrate 14, the titanium bridging member 104 abuts thecontacts 100 to close the test switch arrangement 98. Thus, operation ofthe nozzle arrangement 10 can be tested.

In use, a suitable voltage, typically 3V to 12V depending on theresistivity of the TiAlNi and characteristics of the CMOS drivecircuitry is set up between the active anchor portions 64.1. Thisresults in a current being generated in the inner actuator arms 72 and acentral part of the bridge portion 76. The voltage and the configurationof the inner actuator arms 72 are such that the current results in theinner actuator arms 72 heating. As a result of this heat, the titaniumaluminum nitride of the inner actuator arms 72 expands to a greaterextent than the titanium aluminum nitride of the outer actuator arms 74.This results in the actuator arms 72, 74 bending as shown in FIG. 6.Thus, the dynamic structure 42 tilts towards the wafer substrate 14 toeject the ink drop 58.

A voltage cut-off results in a rapid cooling of the inner actuator arms72. The actuator arms 72 subsequently contract causing the actuator arms72 to straighten. The dynamic structure 42 returns to an originalcondition as shown in FIG. 7. This return of the dynamic structure 42results in the required separation of the drop 58.

The print head chip 12 incorporates a plurality of nozzle arrangements10 as shown in FIG. 1. It follows that, by connecting the nozzlearrangements 10 to suitable micro processing circuitry and a suitablecontrol system, printing can be achieved. A detail of the manner inwhich the nozzle arrangements 10 are connected to such components isdescribed in the above referenced patents/patent applications and istherefore not set out in any detail in this specification. It is to benoted, however, that the ink jet print head chip 12 is suitable forconnection to any micro processing apparatus that is capable ofcontrolling, in a desired manner, a plurality of nozzle arrangements. Inparticular, since the nozzle arrangements 10 span the print medium, thenozzle arrangements 10 can be controlled in a digital manner. Forexample, a 1 can be assigned to an active nozzle arrangement 10 while a0 can be assigned to a quiescent nozzle arrangement 10, in a dynamicmanner.

In the following paragraphs, the manner of fabrication of the nozzlearrangement 10 is described, by way of example only. It will beappreciated that the following description is for purposes of enablementonly and is not intended to limit the broad scope of the precedingsummary or the invention as defined in the appended claims.

In FIGS. 8 and 9, reference numeral 106 generally indicates a complete0.35 micron 1P4M 12 Volt CMOS wafer that is the starting stage for thefabrication of the nozzle arrangement 10. It is again emphasized thatthe following description of the fabrication of a single nozzlearrangement 10 is simply for the purposes of convenience. It will beappreciated that the processing techniques and the masks used areconfigured to carry out the fabrication process, as described below, ona plurality of such nozzle arrangements. However, for the purposes ofconvenience and ease of description, the fabrication of a single nozzlearrangement 10 is described. Thus, by simply extrapolating the followingdescription, a description of the fabrication process for the ink jetprint head chip 12 can be obtained.

The CMOS wafer 106 includes a silicon wafer substrate 108. A layer 110of silicon dioxide is positioned on the wafer substrate 108 to form CMOSdielectric layers. Successive portions of CMOS metal 1, CMOS metal 2/3and CMOS top level metal define an aluminum diffusion barrier 112. Thediffusion barrier 112 is positioned in the layer 110 of silicon dioxidewith a portion 114 of the barrier 112 extending from the layer 110. Thebarrier 112 serves to inhibit the diffusion of ions through the CMOSoxide layers of the layer 110. The CMOS top level metal defines a pairof aluminum electrode contacts 118 positioned on the layer 110.

A layer 116 of CMOS passivation material in the form of silicon nitrideis positioned over the layer 110 of silicon dioxide, the portion 114 ofthe diffusion barrier 112 and the contacts 118. The silicon nitridelayer 116 is deposited and subsequently patterned with a mask 120 inFIG. 10. The silicon nitride layer 116 is the result of the depositionof a resist on the silicon nitride, imaging with the mask 120 andsubsequent etching to define a pair of contact openings 122, alignedacross the wafer 108, an opening 124 for an ink inlet channel to beformed and test switch openings 126.

The silicon dioxide layer 110 has a thickness of approximately 5microns. The layer 116 of silicon nitride has a thickness ofapproximately 1 micron.

In FIGS. 11 and 12, reference numeral 128 generally indicates a furtherfabrication step on the CMOS wafer 106. With reference to FIGS. 8 to 10,like reference numerals refer to like parts, unless otherwise specified.

The structure 130 shows the etching of the CMOS dielectric layersdefined by the layer 110 of silicon dioxide down to bare silicon of thewafer 108.

Approximately 3 microns of resist material 130 is spun onto the siliconnitride layer 116. The resist material 130 is a positive resistmaterial. A mask 132 in FIG. 13 is used for a photolithographic stepcarried out on the resist material 130. The photolithographic image thatis indicated by the mask 132 is then developed and a soft bake processis carried out on the resist material 130.

The photolithographic step is carried out as a 1.0 micron or betterstepping process with an alignment of +/−0.25 micron. An etch ofapproximately 4 microns is carried out on the silicon dioxide layer 110down to the bare silicon of the silicon wafer 108.

In FIGS. 14 and 15, reference numeral 134 generally indicates thestructure 128 after a deep reactive ion etch (DRIE) is carried out onthe silicon wafer 108.

The etch is carried out on the bare silicon of the substrate 108 todevelop the ink inlet channel 22 further. This is a DRIE to 20 microns(+10/−2 microns). Further in this step, the resist material 130 isstripped and the structure is cleaned with an oxygen plasma cleaningprocess.

The etch depth is not a critical issue in this stage. Further, the deepreactive ion etch can be in the form of a DRAM trench etch.

In FIGS. 16 and 17, reference numeral 136 generally indicates thestructure 134 with a first layer 138 of sacrificial resist materialpositioned thereon. With reference to the preceding Figures, likereference numerals refer to like parts, unless otherwise specified.

In this stage, approximately 3.5 microns of the sacrificial resistmaterial 138 is spun on to the front surface of the structure 134. Amask 140 in FIG. 18 is used together with a photolithographic process topattern the first layer 138 of the sacrificial material.

The photolithographic process is a 1.0 micron stepping process orbetter. The mask bias is +0.3 micron and the alignment is +/−0.25micron.

The sacrificial material 138 is a positive resist material. Thesacrificial material 138 can be in the form of a polyimide.

Being a positive resist, the first layer 138, when developed, defines apair of contact openings 142 which provide access to the aluminumelectrode contact layers 122 and a pair of openings 144. The openings142 are positioned between the openings 144 so that the openings 142,144 are aligned across the wafer 108. The openings 144 terminate at thelayer 116 of silicon nitride. As can be seen in the drawings, a regionthat was previously etched into the silicon wafer substrate 108 andthrough the silicon dioxide layer 110 to initiate the ink inlet channel22 is filled with the sacrificial material 138. A region 146 above theportion 114 of the diffusion barrier 112 and the layer 116 is cleared ofsacrificial material to define a zone for the nozzle chamber 34. Stillfurther, the sacrificial material 138 defines a pair of test switchopenings 148.

The sacrificial material 138 is cured with deep ultraviolet radiation.This serves to stabilize the sacrificial material 138 to increase theresistance of the sacrificial material 138 to later etching processes.The sacrificial material 138 shrinks to a thickness of approximately 3microns.

In FIGS. 19 and 20, reference numeral 150 generally indicates thestructure 136 with a second layer 152 of sacrificial resist materialdeveloped thereon. With reference to the preceding figures, likereference numerals refer to like parts, unless otherwise specified.

In this stage, approximately 1.2 microns of the sacrificial resistmaterial 152 in the form of a positive resist material are spun onto thestructure 136. The sacrificial material 152 can be in the form of apolyimide.

A mask 154 shown in FIG. 21 is used together with a photolithographicprocess to pattern the sacrificial material 152. The photolithographicprocess is a 1.0 micron stepper or better process. Further, the maskbias is +0.2 micron for top features only. The alignment during thephotolithographic process is +/−0.25 micron.

It should be noted that, in the previous stage, a relatively deep holewas filled with resist. The sacrificial material 152 serves to fill inany edges of the deep hole if the sacrificial material 138 has shrunkfrom an edge of that hole.

Subsequent development of the sacrificial material 152 results in thestructure shown in FIGS. 19 and 20. The openings 142, 144 are extendedas a result of the mask 154. Further, deposition zones 156 are providedfor the planar sections 80 of the inner actuator arms 72. It will alsobe apparent that a further deposition zone 158 is formed for the fixedpart 36 of the nozzle chamber wall 30. It will thus be appreciated thatthe fixed part 36 is of titanium aluminum nitride. The mask 154 alsoprovides for extension of the test switch openings 148.

Once developed, the sacrificial material 152 is cured with deepultraviolet radiation. This causes the sacrificial material 152 toshrink to 1 micron.

In FIGS. 22 and 23, reference numeral 160 generally indicates thestructure 150 with a third layer 162 of sacrificial resist materialpositioned thereon. With reference to the preceding figures, likereference numerals refer to like parts, unless otherwise specified.

At this stage, approximately 1.2 microns of the sacrificial material 162are spun onto the structure 150. The sacrificial material 162 is apositive resist material. The sacrificial material 162 can be in theform of a polyimide.

A mask 164 in FIG. 24 is used to carry out a photolithographic imagingprocess on the sacrificial material 162.

The photolithographic process is a 1.0 micron stepper or better process.Further, the mask bias is +0.2 micron for the top features only. Thealignment of the mask 164 is +/−0.25 micron.

Subsequent development of the sacrificial material 162 results in thestructure 160 shown in FIG. 22 and FIG. 23.

During this step, the layers 138, 152 and 162 of sacrificial materialare hard baked at 250 degrees Celsius for six hours in a controlledatmosphere. The sacrificial material 162 shrinks to 1.0 micron.

This step results in the formation of deposition zones 166 for theplanar sections 82 of the outer actuator arms 74 and the bridge portion76. This step also results in the formation of a deposition zone for theoutwardly directed re-entrant portion 48 of the fixed part 36 of thenozzle chamber wall 30. Still further, deposition zones 170 for thecontacts 100 for the test switch arrangement 98 are provided.

In FIGS. 25 and 26, reference numeral 172 generally indicates thestructure 160 with a layer of titanium aluminum nitride depositedthereon. With reference to the preceding figures, like referencenumerals refer to like parts, unless otherwise specified.

In this stage, initially, approximately 50 Angstroms of titaniumaluminum alloy at approximately 200 degrees Celsius are sputtered ontothe structure 160 in an argon atmosphere. Thereafter, a nitrogen gassupply is provided and 5000 Angstroms of titanium aluminum is sputteredwith the result that titanium aluminum nitride is deposited on theinitial titanium aluminum metallic layer.

The initial titanium aluminum metallic layer is essential to inhibit theformation of non-conductive aluminum nitride at the resultingaluminum/titanium aluminum nitride interface.

The titanium aluminum is sputtered from a Ti_(0.8)Al_(0.2) alloy targetin a nitrogen atmosphere.

Titanium nitride can also be used for this step, although titaniumaluminum nitride is the preferred material.

Possible new CMOS copper barrier materials such as titanium aluminumsilicon nitride have potential due to their amorphous nanocompositenature. In FIGS. 25 and 26 a layer of titanium aluminum nitride isindicated with reference numeral 174.

The deposition thickness can vary by up to 5 percent.

In FIGS. 27 and 28, reference numeral 176 generally indicates thestructure 172 with the titanium aluminum nitride layer 176 etched downto a preceding resist layer. With reference to the preceding figures,like reference numerals refer to like parts, unless otherwise specified.

At this stage, approximately 1 micron of a positive resist material isspun onto the layer 176.

A mask 178 in FIG. 29 is used together with a photolithographic processto image the positive resist material. The resist material is thendeveloped and undergoes a soft bake process.

The photolithographic process is a 0.5 micron or better stepper process.The mask bias is +0.2 micron for the top features only. The alignment ofthe mask 180 is +/−0.25 micron.

The titanium aluminum nitride layer 174 is etched to a depth ofapproximately 1.5 micron. A wet stripping process is then used to removethe resist. This ensures that the sacrificial material is not removed. Abrief clean with oxygen plasma can also be carried out. This can removesacrificial material so should be limited to 0.2 micron or less.

The result of this process is shown in FIGS. 27 and 28. As can be seen,this process forms the anchor portions 64 and the actuator arms 72, 74together with the bridge portion 76 of the thermal actuator 60. Further,this process forms the fixed part 36 of the nozzle chamber wall 30.Still further, the result of this process is the formation of the testswitch contacts 100.

In FIGS. 30 and 31, reference numeral 180 generally indicates thestructure 176 with a fourth layer 182 of sacrificial resist materialpositioned on the structure 176. With reference to the precedingfigures, like reference numerals refer to like parts, unless otherwisespecified.

In this step, approximately 4.7 microns (+/−0.25 microns) of thesacrificial material 182 is spun onto the structure 176.

A mask 184 shown in FIG. 32 is then used together with aphotolithographic process to generate an image on the sacrificialmaterial 182. The sacrificial material 182 is a positive resist materialand the image generated can be deduced from the mask 184.

The photolithographic process is a 0.5 micron stepper or better process.The mask bias is +0.2 microns. The alignment is +/−0.15 microns.

The image is then developed to provide the structure as can be seen inFIGS. 30 and 31. As can be seen in these drawings, the development ofthe sacrificial material 182 provides deposition zones 186 for atitanium layer that defines the titanium layer 68 of the vias 66 andwhich serves to fix the anchor portions 64 of the thermal actuator 60 tothe silicon nitride layer 26. The sacrificial material 182 also definesa deposition zone 188 for the titanium layer 68 of the fulcrum formation92. Still further, the sacrificial material 182 defines a depositionzone 190 for titanium of the movable part 38 of the nozzle chamber wall30. Still further, the sacrificial material 182 defines deposition zones192 for the test switch arrangement 98.

Once the sacrificial material 182 has been developed, the material 182is cured with deep ultraviolet radiation. Thereafter, the sacrificialmaterial 182 is hard baked at approximately 250 degrees Celsius in acontrolled atmosphere for six hours. The resist material 182subsequently shrinks to approximately 4 microns in thickness.

In FIGS. 33 and 34, reference numeral 194 generally indicates thestructure 180 with a layer 196 of titanium deposited thereon.

At this stage, approximately 0.5 micron of titanium is sputtered on tothe structure 180 at approximately 200 degrees Celsius in an argonatmosphere.

It is important to note that the mechanical properties of this layer arenot important. Instead of titanium, the material can be almost any inertmalleable metal that is preferably highly conductive. Platinum or goldcan be used in conjunction with a lift-off process. However, the use ofgold will prevent subsequent steps being performed in the CMOSfabrication. Ruthenium should not be used as it oxidizes in subsequentoxygen plasma etch processes which are used for the removal ofsacrificial materials.

The deposition thickness can vary by 30% from 0.5 micron and remainadequate. A deposition thickness of 0.25 micron should be achieved inany holes.

In FIGS. 35 and 36, reference numeral 198 generally indicates thestructure 194 with the layer 196 of titanium etched down to thesacrificial layer 182.

At this stage, approximately 1 micron of resist material is spun on tothe layer 196. A mask 200 shown in FIG. 37 is then used together with aphotolithographic process to form an image on the layer 196.

The resist material is a positive resist material. It follows that theimage can be deduced from the mask 200. It should be noted that allvertical geometry is masked. It follows that there are no etches ofsidewalls.

The photolithographic process is a 1.0 micron stepper process or better.Further, the mask bias is +0.3 micron and the alignment of the mask is+/−0.25 micron.

The resist material is developed and undergoes a soft bake process. Thetitanium layer 196 is etched down to the preceding sacrificial layer182. The sacrificial layer 182 was hard baked. This hard baking processinhibits the sacrificial layer 182 from being etched together with thetitanium layer 196.

The etching process is planar and the lithographic process is thereforenot critical.

The resist material is then removed with a wet stripping process. Thisensures that the sacrificial material is not also removed. Thereafter,the front side of the structure is cleaned in oxygen plasma, ifnecessary. It should be noted that oxygen plasma cleaning would stripthe resist material. It follows that the oxygen plasma stripping orcleaning should be limited to 0.2 micron or less.

The result of this process can clearly be seen in FIGS. 34 and 35. Inparticular, the deposition zones 186, 188, 190, 192 are now each coveredwith a layer of titanium.

In FIGS. 38 and 39, reference numeral 202 generally indicates thestructure 198 with a layer 204 of low temperature silicon nitridedeposited thereon. With reference to the preceding figures, likereference numerals refer to like parts, unless otherwise specified.

At this stage, the layer 204 of low temperature silicon nitride having athickness of approximately 1.5 microns is deposited through ICP chemicalvapor deposition (CVD) on the structure 198 at approximately 200 degreesCelsius.

Any suitably strong, chemically inert dielectric material could be usedinstead. The material properties of this layer are not especiallyimportant. The silicon nitride does not need to be densified. It followsthat high temperature deposition and annealing are not required.Furthermore, this deposition process should be approximately conformalbut this is not particularly critical. Still further, any keyholes thatmay occur are acceptable.

In FIGS. 40 and 41, reference numeral 206 generally indicates thestructure 202 with a nozzle rim 208 etched into the layer 204. Withreference to the preceding figures, like reference numerals refer tolike parts, unless otherwise specified.

In this step, approximately 1 micron of resist material is spun on tothe structure 202. A mask 210 in FIG. 42 is used together with aphotolithographic process to form an image of the nozzle rim 94 on theresist material.

The photolithographic process is a 1.0 micron stepper process or better.Further, the mask bias is +0.2 microns and the alignment is +/−0.25microns.

The resist material is developed and undergoes a soft bake process. Theresist material is a positive resist material and it follows that theresultant image can be easily deduced from the mask 210.

The layer 204 of silicon nitride is then etched to a depth of 0.6 micron+/−0.2 micron so that a recess 212 to be positioned about the nozzle rim94 is formed.

It will be appreciated that this process is an initial stage in theformation of the roof wall 32 as described earlier.

The resist material is wet or dry stripped.

In FIGS. 43 and 44, reference numeral 214 generally indicates thestructure 206 subsequent to the layer 204 of silicon nitride beingsubjected to a further etching process. With reference to the precedingfigures, like reference numerals refer to like parts, unless otherwisespecified.

At this stage, approximately 1.0 micron of resist material is spun ontothe structure 206. A mask 216 shown in FIG. 45 is used together with aphotolithographic process to form an image on the layer 204.

The resist material is a positive resist material. It follows that theimage can easily be deduced from the mask 216.

The photolithographic process is a 0.5 micron stepper process or better.Further, the mask bias is +0.2 micron and the alignment is +/−0.15micron.

The image is then developed and undergoes a soft bake process.Subsequently, a timed etch of the silicon nitride takes place to anominal depth of approximately 1.5 microns.

The result of this process is clearly indicated in FIGS. 43 and 44. Ascan be seen, this process results in the sandwiching effect created withthe anchor portions 64 of the thermal actuator 60, as described earlierin the specification. Furthermore, the silicon nitride of the fulcrumformation 92 is formed. Still further, this process results in theformation of the roof wall 32 and the extended portion 102 of the roofwall 32. Still further, development of the image results in the creationof the ink ejection port 44.

It is to be noted that alignment with the previous etch is important.

At this stage, it is not necessary to strip the resist material.

In FIGS. 46 and 47, reference numeral 218 generally indicates thestructure 214 with the wafer substrate 108 thinned and subjected to aback etching process.

During this step, 5 microns (+/−2 microns) of resist 220 are spun on toa front side 222 of the structure 214. This serves to protect the frontside 222 during a subsequent grinding operation.

A back side 224 of the CMOS wafer substrate 108 is then coarsely grounduntil the wafer 108 reaches a thickness of approximately 260 microns.The back side 224 is then finely ground until the wafer 108 reaches athickness of approximately 260 microns. The depth of the grindingoperations depends on the original thickness of the wafer 108.

After the grinding operations, the back side 224 is subjected to aplasma thinning process that serves to thin the wafer 108 further toapproximately 200 microns. An apparatus referred to as a Tru-SceTE-2001NT or equivalent can carry out the plasma thinning process.

The plasma thinning serves to remove any damaged regions on the backside 224 of the wafer 108 that may have been caused by the grindingoperations. The resultant smooth finish serves to improve the strengthof the print head chip 12 by inhibiting breakage due to crackpropagation.

At this stage, approximately 4 microns of resist material is spun on tothe back side 224 of the wafer 108 after the thinning process.

A mask 226 shown in FIG. 48 is used to pattern the resist material. Themask bias is zero microns. A photolithographic process using a suitablebackside mask aligner is then carried out on the back side 224 of thewafer 108. The alignment is +/−2 microns.

The resultant image is then developed and softbaked. A 190 micron, deepreactive ion etch (DRIE) is carried out on the back side 224. This isdone using a suitable apparatus such as an Alcatel 601E or a SurfaceTechnology Systems ASE or equivalent.

This etch creates side walls which are oriented at 90 degrees +/−0.5degrees relative to the back side 224. This etch also serves to dice thewafer. Still further, this etch serves to expose the sacrificialmaterial positioned in the ink inlet channel 22.

In FIGS. 49 and 50, reference numeral 228 generally indicates thestructure 218 subjected to an oxygen plasma etch from the back side 224.

In this step, an oxygen plasma etch is carried out to a depth ofapproximately 25 microns into the ink inlet channel 22 to clear thesacrificial material in the ink inlet channel 22 and a portion of thesacrificial material positioned in the nozzle chamber 34.

Etch depth is preferably 25 microns +/−10 microns. It should be notedthat a substantial amount of over etch would not cause significantproblems. The reason for this is that this will simply meet with asubsequent front side plasma etch.

Applicant recommends that the equipment for the oxygen plasma etch be aTepla 300 Autoload PC or equivalent. This provides a substantiallydamage-free “soft” microwave plasma etch at a relatively slow rate being100 to 140 nanometers per minute. However, this equipment is capable ofetching 25 wafers at once in a relatively low cost piece of equipment.

The oxygen should be substantially pure. The temperature should notexceed 140 degrees Celsius due to a thermally bonded glass handle wafer.The time taken for this step is approximately 2.5 hours. The processrate is approximately 10 wafers per hour.

In FIGS. 51 and 52, reference numeral 230 generally indicates thestructure 228 subsequent to a front side oxygen plasma etch carried outon the structure 228.

During this step, the structure 228 is subjected to an oxygen plasmaetch from the front side 222 to a depth of 20 microns +/−5 microns.Substantial over etch is not a problem, since it simply meets with theprevious etch from the back side 224. It should be noted that this etchreleases the MEMS devices and so should be carried out just before guardwafer bonding steps to minimize contamination.

The Applicant recommends that an apparatus for this step be a Tepla 300Autoload PC or equivalent. This provides a substantially damage-free“soft” microwave plasma etch at a relatively slow rate of between 100and 140 nanometers per minute. The slow rate is countered by the factthat up to 25 wafers can be etched at once in a relatively low costpiece of equipment.

The oxygen should be substantially pure. The temperature should notexceed 160 degrees Celsius. The process takes about two hours and theprocess rate is approximately 12.5 wafers per hour.

During testing, the nozzle arrangement 10 was actuated withapproximately 130 nanojoules for a duration of approximately 0.8microseconds.

It should be noted that the test switch arrangement 100 does not quiteclose under normal operation. However, when the nozzle arrangement 10 isoperated without ink or with a more energetic pulse, the test switcharrangement 100 closes.

It was found that the ejection of ink occurred approximately 4microseconds after the start of an actuation pulse. Drop release iscaused by the active return of the actuator to the quiescent position asthe actuator cools rapidly.

Turning to FIGS. 53 and 54, there is shown an alternative embodiment ofthe invention in which reference numerals used in other Figures are usedto indicate like features. It will be appreciated that these Figures areschematic in nature, in order to illustrate the operation of theembodiment, and are not intended to represent actual structural details,including the specifics of construction type and materials choice. Thoseskilled in the art will be able to determine appropriate constructiontechniques and material choices by referring to the main embodiment andother construction techniques described in the cross-referenceddocuments.

The nozzle arrangement 232 of FIGS. 53 and 54 differs from the mainembodiment in that an operative end 234 of the dynamic structure 42 isenclosed within the nozzle chamber 34, and the ink ejection port 44 isformed above it in a roof portion 236 that partially defines the nozzlechamber 34.

In operation, the operative end 234 of the dynamic structure 42 moves up(rather than down, as in the other embodiment) relative to the substrate14, which causes an increase in fluid pressure in the region between theoperative end 234 and the roof portion 236. Whilst there is a gap 238between an edge 240 of the operative end 234 and the walls of the nozzlechamber 34, this is considerably smaller in area than the ink ejectionport 44. Accordingly, whilst there is some back-leakage of ink past theoperative end 234 through the gap 238 during actuation, considerablymore ink is caused to bulge out of the ink ejection port 44, as shown inFIG. 54.

As drive current through the active portions 64.1 is stopped, theoperative end 234 stops moving towards the roof portion, then begins tomove back towards the quiescent position shown in FIG. 53. This causes abulging, thinning, and breaking of the ink extending from the nozzle asshown in FIG. 7, such that an ink droplet continues to move away fromthe ink ejection port 44. Refill takes place as described in the mainembodiment, and the nozzle arrangement is then ready to fire again.

Although the invention has been described with reference to specificembodiments, it will be appreciated by those skilled in the art that theinvention can be embodied in many other forms.

1. A nozzle arrangement for an inkjet printhead, said nozzle arrangementcomprising: a substrate with side walls and a roof portion togetherforming an ink chamber, the substrate defining an ink supply channelleading to the ink chamber, with one side wall defining an aperture; anelongate actuator extending through said aperture into the ink chamber;a dynamic structure cantilevered from the side wall below the aperture;a static structure cantilevered from the side wall below the dynamicstructure, wherein the actuator is connected to the dynamic and staticstructures at a point distal from the aperture such that thermalexpansion of the dynamic structure moves the actuator upwards in thechamber to eject ink from the chamber via a port defined in the roofportion.
 2. The nozzle arrangement of claim 1, in which the ink supplychannel defined in the substrate is the result of a back-etching processcarried out on the substrate.
 3. The nozzle arrangement of claim 1, inwhich CMOS dielectric layers are positioned on the substrate, with CMOSmicro-processing drive circuitry being positioned on the CMOS dielectriclayers.
 4. The nozzle arrangement of claim 3, in which a metal diffusionbarrier is positioned in the dielectric layers about the ink supplychannel.
 5. The nozzle arrangement of claim 1, in which the staticstructure defines a fixed part of the chamber side wall and the dynamicstructure defines a movable part of the chamber side wall and the roofwhich defines the ink ejection port.
 6. The nozzle arrangement of claim5, in which the movable part of each chamber wall overlaps the fixedpart of the nozzle chamber side wall.
 7. The nozzle arrangement of claim6, in which the fixed part of the chamber side wall defines an inwardlydirected lip that extends into the nozzle chamber and an outwardlydirected, re-entrant portion that terminates in a radially extendingrim, the moveable part depending from the roof portion and terminatingat a free edge, so that the re-entrant portion and the free edge candefine a fluidic seal when the chamber is filled with ink via the supplychannel.